Cleft palate is among the major craniofacial defects occurring in humans. Successful palatal fusion requires the appearance of a glycoprotein coat on cells of the palate's medial edge epithelium (MEE), and subsequent lysosomalmediated autolysis of the MEE. Cell death inhibitors prevent complete fusion of palatal shelves and may eliminate the MEE's glycoprotein coat. Scanning electron microscopy studies show fusion-related surface changes appearing first in the region of the MEE that will fuse first. Scanning electron microscopy evaluation of a cell's carbohydrate coat has recently been made possible by lectin-microsphere conjugates. Lectins are bound to the aldehyde groups of specially treated microspheres, and the resulting conjugates are allowed to bind to cell surfaces. SEM evaluation of the number and location of bound microspheres provides information about the glycoprotein coat not determinable by other methods. In this investigation, lectin-coated microspheres will be used to study the in vitro development of the glycoprotein coat of the embryonic mouse palate and the effect of cell death inhibitors on SEM surface changes and lectin-binding in the palatal MEE.